Thermostatic electric switch



Dec. 14, 1926. 1,610,915

J. M. ALLEN C THERMOSTATIC ELECTRIC SWITCH Filed Nov. 2, 1925 M M HMH Patented Dec. 14, 1926.

UNITED STATES PATENT OFFICE. j

yJAMES M. ALLEN, OF ST. LOUIS', MISSOURI, .ltSSIG-ll'OR` OF ONE-HALF TO THE SUPERIOR BRASS & MFG. CO., OF ST. LOUIS, MISSOURI, A CORPORATION OF MISSOURI.

THERMOSTATIC ELECTRIC SWITCH.

Application filed November 2, 1925.

My invention relates to improvements in thermostatic electric switches, and has for its primary object a switch which will automatically break an electric circuit when a predetermined temperature has been reached.

A further object is to construct an electric switch for use on electric heating appliances of all kinds to prevent overheating of the heating element and the consequentburning out of the same.

YA still further object is to construct a device which is set and tested for a predetermined temperature at the factory, thus obviating the necessity of making any adjustments after the device is delivered. By preventing overheating of the heating element the danger of lire caused by leaving the device unattended with the electric current turned on is eliminated. In this con nection, it is especially useful for electric irons, which are the most frequent cause of tire occasioned by this neglect.

My device is also useful in, hospitals or in the home for electric heating pads or other heating and baking devices used on patients, as it will preventany possibility of injuring the patient due to excessive heat, and when used in hospitals a number of different switches, which have had the temperature accurately regulated, can be used on the same instrument so as to cover a wide range of heat and meet all necessary requirements. `Another' advantage of my device is that it can be placed anywhere in the line and does not have to be built in the device so that it can be sold separately and used for a great number of purposes. In fact my device can be practically termed an accessory for electric heatingdevices of all kinds and can be utilized either in a hospital, in the kitchen, for laundry purposes, or for heating regardless of the construction of the device.

In the drawings 1'- Fig. l is a top-plan view of my device with portions broken away and portions in sec tion. and taken preferably on the line 1-1 of 2;

Fig. 2 is a side elevation of my device with portions broken away and in section;

Fig. 3 is a top plan view of my complete device;

Fig. 4 is a vertical cross section taken on the line l-/i of Fig. 1;

Serial No. 66,242.

Fig. 5 is an end view, viewing the same in the direction of the arrow 5 of Fig. 1;

Fig. 6 is a perspective view of the bracket to which the thermostatic arm is attached;

Fig 7 is a perspective view of the container for the resistance element;

Fig 8 is a perspective view of one of the conductors employed in the push socket;

Fig. 9 is a perspective view of the conductor employed when a screw socket is used; and

Fig. 10 is a cross section of the cover taken on the line 10-1O of Fig. 3.

In the construction of my device, I employ a base 11, which is provided at each end with projections 12 and 13. j ections are preferably formed integral with the base, which-is Vconstructed of any suitable insulating material of the kind which will not be softened or become deteriorated from heat. The projection 12 is prefer ably provided with screw-threads over which is secured a jacket or sleeve 1li of conducting material. These screw threads are so formed that the sleeve 14 can be readily inserted in the ordinary lamp socket. The projection 12 is also provided with a central bore 15 through which a screw 15 extends. Held in position against the end of the projection 12 by means of the screw 16 is a contact plate 17. The opposite end of the screw 16 is screw threaded and seated in thc projection 18 of the electric conductor 19. This electric conductor is in turn secured to a conductor 20 by means of a screw and nut 21. Projecting upward from the conductor 20 is a screw 22, which is secured to the conductor by means of the nut* 23. The screw 22 projects above the nut 23 a considerable distance 'as is clearly illustrated in Figs, 2 and 4, the purpose -f of which will be explained in detail later.

Spaced apart from the screw 22 is a secondA screw 24, which has a nut 25 threaded thereon and which secures one end of the conductor 26 to the base 11, A second screw 27 and nut 28 secure the same conductor to the base adjacent its opposite end. The projection 13 is provided with slots 29 and 30. Into the slot 30 extends the end 31 of the conductor 26. This end or tongue 31 is bowed as illustrated in Fig. 1 and is of These pro- 7 resilient material so that it can engage with one tongue of a plug not shown. The purpose of this engagement will be 'explained in detail later.

The sleeve 14 is provided' with an eX- tension 32, which is secured to the projection 33 formed on the container 34 for the resistance element. These two portions are united by means of a screw 35 and nut 36 or similar securing means. Within the container 34 is placed a resistance element 37, which is formed of any well-known material that will oiler a resistance to the electrical current and become heated thereby. Resting on the resistance element isa metallic roller 38, which is pivotal'ly carried by a thermostatic arm 39. This thermostatic arm is constructed of layers of metal which have a different co-eiiicient of expansion so that upon becoming heated the arm will bend out of its normal position. The purpose of this bending will be explained in detail later. The arm 39 isI secured to the upwardly extending portion 40 of the bracket 41. This bracket is lin turn secured to the conductor 42 by means of the screw 43 and nut 44. The conductor 42 is also provided with a tongue 45, which is located in the opening or slot 29. This tongue has the same shape as the tongue 31. lt is also adapted to engage with the projecting portion ot a push plug. Tn order to make the action of the arm more positive, a plurality of thermostatic strips 46 are secured to the arm 39 by means of a rivet or similar fastening means 47. Secured to the arm 39 is a block of insulating material 48. This block is secured by means of a screw 49, which passes through the arm 39 and through the strips 46. The block 48 is so arranged as to have its end 50 contact with a conductor rod '51. This conductor rod is secured inthe arms 52 of a spring 53. This spring is mounted in a recess 54 formed in one side of the blockand is held in position by means of the screw 55. The conductor rod 51 is adapted to contact with the screws 22 and 24 and complete the electric circuit across the gap.

After the device has been thus far assembled, vthe working parts are enclosed by means of a cover having a top 56, sides 57 andyends 58 and 59. The top 56 of the cover is provided with a plurality of vents 60 so as to allow the escape of heated air. It will be noted that the ends 58 and 59 are of less depth than the sides 57 so that these endsv will rest on the top face of the block 11.V They will also be located on the inside tace of the projections 12 and 13, thus acting as a reinforcement for these projections and preventing them from being readily snapped off. The end 58 is provided with a cutaway portion 61,' which permits the screw 16 to pass therethrough and with a cutaway portion 62 to permit'the electrode or conductor 32 to pass therethrough, while the end 59 is provided with cutaway portions to permit the tongues 3l and 45 t-o pass therethrough.

The operation of my device is as follows; After the various parts have been assembled, the one end of theswitch is secured in position in an electric socket. A push plug carrying an electric` conductor, which conductor in turn is secured to a heating unit, is inserted in the opposite end, the electric current turned on, and the device is ready for operation. The electric current passing through the msistance element 37 causes the same to become heated. This heat is in turn transmitted to the metallic roller 38 and from there to the thermostatic arm 39. rl`his thern'iostatic arm is so arranged that the outside port-ion thereof, that is the portion nearest the screws 22 and 24, does not expand as readily yas the inside portion, and upon becoming heated causes unequal expansion, and thus torces the insulation block 48 toward the conductor rod 5l. This expansion continues until the end 50 ofthe block 48 contacts with the rod 51 and upon any further expansion the conductor rod 5l, which has been previously in contact with the screws 22 and 24, will be separated therefrom, thus ibreaking the current. As soon as the current has become broken. the resistance element 37 will commence to cool because no, more current is passing therethrough. This will permit the different'laminations of the thermostatic arm to contract and bring it back to its original position, thus automatically restoring the electric current. p

Tt is not necessary in m device to utilize a different construction o thermostatic arm for various temperatures because, by loosening the nut 44 and swinging the arm in the direction indicated by the arrow A. a greater' amount of heat is necessary to break the circuit as the thermostatic arm 39 must move through a greater arc before the conductor rod 51 can be moved away from the screws 22 and 24 whereas, if a lower temperature is required, the thcrmostatic arm 39 is moved in the direction of the arrow B and consequently a less degree of expansion will be re uired to break the circuit. Therefore it wil be readily seen that I can adjust my device so as to make and break the connection at any predetermined temperature, and it is my intention to manufacture my devices and set them for certain degrees of temperature, which degree will be clearly stated on the cover, referably by molding the degree therein. l) do not, however, desire to limit myself to this feature of set-ting the device at the factory because the regulation may be made by the person using the same, the essential feature being to break the electric current when a desired temperlun ature `has been reached and to do this by means of a device which can be located anywhere in the electric line so that it will not be necessary to purchase a device having a built-in therinostatio control.

Neither do l desire to limit myself to the precise construction shown for the projections 12 and 13, as both of these may be arranged for push plugs, or bothmay be arranged Jtor screw sockets. They may also be changed end for end or the electric conductors may be permanently secured to one end Without departing from the spirit of niv invention.

.v'aving uiiy described my invention, what claim is:-

l. A. thermostatic switch comprising a base, a conductor provided with a resistance element carried by said base, a second conductor carried by said base, a thermostatic arm carried byl said' second conductor and arranged for constant contact with said resistance element, a pair of conductors carried by said base and having their adjacent ends spaced apart thereby forming a gap, movable rneans for bridging said gap, and means carried. by the thermostatic arm and adapted to contact with said movable means for operatingsaine whereby the gap is opened and closed. y

2. A thermostatic switch comprising a base, a conductor provided with aA resistance eieinent carried by said base, a second conductor carried by said base, a thermostatic arm carried by said second conductorJ a roller carried by the thermostatic arm and adapted to be in contact With said resistance eiement "whereby i c' is conducted therefrom' to said therin ic arm, a pair of conductors carbase and having;` their adjacent d apart-thereby forming a gap, means for bridging said gap, and

operated by the thermostatic arm said movabie means is actuated rebu ciosing said gap e. thermostatic switch comprising a base., conductor provided with a resistance alternent carried thereby, a second conductor carried by said base, a thermostatic arm arranged for', constant contact with said resistance element carried by the second nientioned conductor, a pair of conductors carried by said base and having their ad]acent ends spaced apart thereby forming a gap.- spring-held means for closing said gap, and

conductor, means carried by said thermostatic arm for making a constant Contact with said resistance element, said means adapted to conduct heat from said element to said arm,`a pair of longitudinally spaced apart conductors carried by said base, movable means carried by the base for making and breaking an electric circuit through said last mentioned conductors, and means carried by said thermostatic arm for actuating said movable means.

5. A thermostatic switch comprising a base, electric conductors carried by said base, a thermostatio arm located in one ot said conductors, a resistance eiement iocated in said conductor and in constant contact with said thermostatic arm whereby. said arm is heated by conduction, a gap formed in the other of said conductors, movable means for bridging said gap tor completing an electric-circuit, insulating means carried by said tbermostatic arm oricontacting with and operating said movable means whereby an,

electric circuit is completed or interrupted, and means carried by each end of said base and connected to said electric conductors 9 whereby the switch can be connected to a source of energy and to a translatino device.

In testimony ivhereoi` have alxed my signature.

JAMES Ml ALLEN. 

